Fused salt bath for electrodeposition of transition metals



FUSED SALT BATH FOR ELECTRODEPOSITION F TRANSITION METALS Eugene Wainer, Cleveland Heights, Ohio, assignor, by mesne assignments, to Horizons Titanium Corporation, Princeton, N.J., a corporation of New Jersey No Drawing. Application July 16, 1954 Serial No. 443,969

12 Claims. (Cl. 20464) This invention relates to the production of halides of the transition metals titanium, zirconium, hafnium, niobium, vanadium and tantalum. More particularly, it relates to the production of transition metal halides by halogenation of the transition metal carbides in fused salt baths.

The halides of the transition metals titanium, zirconinm, hafnium, niobium, vanadium and tantalum are useful for a variety of purposes including the preparation of other compounds of these transition metals, the preparation of alloys of the transition metals and other metals, and the preparation of the transition metals in pure metallic form. For example, in the copending applications of Merle E. Sibert and John T. Burwell, Serial Nos. 358,194 and 383,401, new Patent No. 2,828,251, there are described methods of producing cathode deposits and cladding deposits of these transition metals by electrolysis in a fused halide salt bath in which is immersed a solid anode composed of the carbide of the transition metal or a mutual solid solution of the carbide and monoxide of the transition meal. Broadly speaking, in these processes the source of the electro-deposited transition metal is the transition metal component of the metalliferous anode immersed in the bath. The chemistry of the electrolysis, however, appears to involve reaction between the transition metal component of the anode and the fused halide salt bath with the resultant formation of a transition metal halide that is then electrolytically decomposed at the cathode with the deposition of the transition metal on the cathode and the reconstitution of the original halide salt constituents of the bath. Although the methods described in the Sibert and Burwell applications produce the desired transition metal without significant impairment of the original overall composition of the fused salt bath, they do require intermittent replenishment of the anode material in order to provide a source of transition metal that will combine with the halide salt component of the bath to form a transition metal halide that can be decomposed at the cathode. Moreover, the necessity for dissolving the transition metal component of the anode in the fused salt bath as an integral part of the electrolytic operation imposes important procedural limitations on the electrolysis and, in particular, limits the concentration of the transition metal halide that can be built up in the bath.

I have now found it possible to produce transition metal halides by the halogenation of solid transition metal compounds in fused halide salt baths. The transition metal halide product of my process can be recovered from the fused salt bath in which it is formed or, advantageously, the fused bath containing the transition metal halide can be used directly as a cell feed material in electrolytic processes of the type known as electro winning for producing transition metal cathode deposits under conditions such as those setforth in the aforementioned applications. A number of advantages follow from the establishment of the electrolytically decomposable transition metal halide content of fused salt baths "ice at independently of the electrolysis operation. One of the most important of these advantages is the significant increase in the concentration of the transition metal halide in the bath that can be attained. The increase in concentration of the transition metal halide content of they at which this transition metal halide can be electrolytically decomposed and the transition metal constituent thereof electrodeposited at the cathode. Moreover, the formation of the electrolysis bath extraneously of the electrolysis operation makes possible a cyclic process wherein a fused salt bath high in transition metal content is continuously fed to the electrolytic cell and the fused salt depleted of its transition metal content is continuously withdrawn therefrom for replenishment of its transition metal content in accordance with the method of my invention.

The method of the present invention is thus concerned with the production of transition metal halides in fused salt baths, particularly those transition metal halides which are in a form capable of being cathodically deposited during used sale electrolysis of the type known as electrowinning. My novel method comprises preparing a fused salt bath composed of either an alkali metal halide or an alkaline metal halide, or both, and advantageously further containing a halide of the transition metal. There is then introduced into the fused salt bath a solid carbide product composed of the carbide of the transition metal or a mutual solid solution of the carbide and the monoxide of the transition metal. introduced into the resulting solid-containing fused salt bath until the transition metal content of the solid carbide product has been substantially completely converted to the halide thereof in solution in the fused salt bath. The halogenation is carried out at a temperature within the range of about 600 to 1100 C. The product of the halogenation of the solid-containing fused salt bath depends upon the transition metal and halogen gas employed, the composition of the fused salt bath, and the temperature at which the halogenation is carried out. In general, for those transition metals which are capable of forming lower valent halide compounds, the valence of the transition metal halide resulting from the halogenation of the bath depends upon the temperature of the bath, higher operating temperatures ordinarily resulting in lower valent transition metal products. In the case of the transition metals which are incapable of forming multi-valent halide compounds, the product of the halogenation is the normal halide of the transition metal. The transition metal halide is ordinarily recovered from the fused salt bath in the form of a complex of the transition metal halide with one or more of the halide salt constituents of the bath.

The method of my invention is equally applicable to the production of any of the halides of the transition metals, titanium, zirconium, hafnium, niobium, vanadium and tantalum. In the case of the transition metals Where a number of valence forms are capable of existing, I havefound that the halide may be formed and dissolved in the fused salt bath in any of the lower valence conditions.

Thus, in the case of titanium as representative of the multi-valent transition metals, both tit-anum dichloride and titanium tri-chloride may be formed, and the formation of the diflicultly soluble and highly volatile titanium tetrachloride may actually be minimized by control of the conditions under which halogenation is carried out. With regard to the transition metals zirconium and hafnium which form no lower valent halides, the halogena-- tion results in the formation only of a tetravalent transition metal halide. Inasmuch as the production of titanium halide in the fused salt bath is representative of the production of corresponding transition metal halides in: the bath, the following discussion will be directed to the I Patented July 14, 19 59 A halogenating gas is then titanium aspect of the invention in the interest of simplicity. However, it must be understood that what is said with respect to the production of titanium halides applies with equal force and effect to the production of the corresponding halides of the other transition metals, titanium, zirconiunnhafnium, niobium, vanadium and tantalum.

The fused salts in which the titanium halide is formed pursuant to my invention may comprise one or more of the alkali metal halides such as lithium, sodium and potassium chlorides, bromides, iodides and fluorides or one or more of the alkaline earth metal halides such as calcium, barium, strontium and magnesium chlorides, bromides, iodides and fluorides, or mixtures of one or more of each of these alkali metal halides and alkaline earth metal halides. In addition to the aforementioned alkali and alkaline earth metal halides, titanum halides (particularly double halides of titanium and an alkali metal) may be incorporated in the bath. It should be noted, however, that if both a titanium double fluoride and an alkaline earth halide other than a fluoride are present inthe molten bath, there is a pronounced tendency for these two compounds to react and evolve the vapors of a halide other than the fluoride of titanium. Accordingly, in order to minimize loss of titanium from the bath in this way, it is advisable not to use this combination of bath components, although it must be understoodthat such a combination is operative even though extravagant of titanium halide. However, all of these alkali and alkaline earth metal halides and mixtures thereof are capable of holding a significant amount of titanium halide in solution, either as a simple titanium halide dissolved in the fused salt bath or, more commonly, as a complex salt of the titanium halide and one or more of the halide salt constituents of the bath. Therefore, the bath constituents may be deliberately chosen for those halide salts which readily form complex salts with the titanium halides produced by my process. In the case of many of the titanium halides (and other transition metal halides) produced by the method of my invention, selection of bath constituents which readily form such complex salts is desirable, particularly in the case of bromide and iodide salts which are relatively unstable at the high temperatures encountered in the operation of my process, With regard to the choice of a halide salt suitable for forming complex salts with the titanium halide product, I have found it advantageous to use an alkali or alkaline earth metal halide containing the same halogen as the halide to be prepared. Thus, in the case of the preparation of, say, a titanium fluoride, I have found that sodium and potassium fluorides readily combine with the titanium fluoride produced to form complex alkali metal double fluorides of titanium.

The components of the fused salt should be of high purity and should be substantially completely anhydrous in order to minify the introduction of extraneous impurities, including oxygen, into the electrodeposited titanium which is produced by the subsequent electrolysis of the titanium-containing fused salt bath. The alkali metal halides and alkaline earth metal halides are commercially available in a state of purity adequate for use in the practice of the method of my invention. If titanium halides, for example, an alkali metal fluotitanate, are used in compounding a fused salt mixture in practicing the invention, these salts should be of recrystallized quality in order to avoid the inclusion of the impurities normally present in these salts as initially produced.

Fusion of the components of the salt bath is carried out under conditions which will insure the absence of atmospheric oxygen and moisture. Thus, I have found it advantageous to carry out this fusion in a closed reaction vessel in which an inert atmosphere of argon or the like may be maintained. The salt in the reaction vessel maybe heated by any means which will not introduce .4 impurities thereinto. For example, the exterior of the reaction vessel, which should be formed of a corrosion resistant material such as graphite or the like, may be heated by any suitable means. On the other hand, the salt may be heated by electric resistance elements within the reaction vessel itself or by means of an alternating curent passing through electrodes immersed in the salt. The salt should be heated to a temperature at least 50 C., and advantageously about C., above its fusion point in order to insure adequate fluidity of the fused mass. The temperature of the bath should be within the range of about 600 to 1100 C., the lower limit of the temperature of the bath being determined to a large extent by the temperature at which the bath has the requisite fluidity and the upper limit of bath temperature being that at which volatilization of the fused salt becomes prohibitive.

With regard to the actual operating temperature of the bath, I have found that, in the case of those transition metals whose compounds exist only in a single valence state, only those halides in which the transition metal has that single valence will be formed, irrespective of the temperature at which the halogenation is carried out. However, in the case of the multi-valent transition metals, 1 have found that the transition metal halide is formed and dissolved in the bath either as the di-halide, the trihalide, the tetra-halide, the penta-halide, or mixtures thereof depending upon the transition metal and the temperature of the bath employed. For example, the halogenation of a solid titanium carbide material in a fused halide salt bath at a temperature within the range of about 700 to 900 C. favors the formation of trivalent titanium halides and halogenation at a temperature within the range of amout 900 to 1100 C. favors the formation of. divalent titanium halides. At temperatures below about 700 C. tetravalent titanium halides tend to be the principal product of the halogenation operation.

Similarly, in the halogenation of niobium in accordance with my invention, temperatures within the range of about 600 C. to 700 C. result in the formation of pentavalent niobium halides, temperatures within the range of about 700 to 900 C. result in the formation of tetravalent niobium halides, and temperatures within the range of 900 to 1100 C. result in the formation of divalent niobium halides. In the halogenation of vanadium, temperatures within the range of about 650 to 750 C. result in the formation of tetravalent vanadium halides, temperatures within the range of about 750 to 850 C. result in the formation of trivalent vanadium halides, and temperatures within the range of about 850 to 1000 C. result in the formation of divalent vanadium halides. In the halogenation of tantalum, temperatures within the range of about 700 to 1100 C. result in the formation of pentavalent tantalum halides, the lower valent tantalum compounds apparently being oxidized to the penta-valent state as rapidly as they are formed. In the case of zirconium and hafnium, only tetravalent zirconium and tetravalent hafnium halide compounds can be formed, irrespective of the temperature at which the halogenation is conducted.

The formation of the titanium halide in the fused salt bath is accomplished by halogenating a solid titanium carbide material in situ in the bath. These carbide materials include, as described in the aforementioned Sibert and Burwell applications, titanium carbide itself and a mutual solid solution of titanium carbide and titanium monoxide. Although the dense form of the titaniumcarbide described in the aforementioned application may be used satisfactorily in practicing my invention, I presently prefer to produce the carbide in a less dense form so that it will have a degree of porosity which will promote more rapid chlorination of its transition metal component in the fused salt. The production of such a less dense form of the titanium carbide is described in the copending application of Bertram C. Raynes, Merle E. Sibert and John T. Burwell, Jr., Serial No. 398,191, filed December 14, 1953, "and the lower practical limit for the density of such a porous carbide is that which will insure adequate mechanical strength for convenient handling. However, there is no lower limit for the density of the carbide or carbide-monoxide solid solution with respect to their reactivity and utility.

The solid titaniferous material may be introduced into the fused salt bath either in the form of relatively large lumps or in the form of smaller lumps of about A inch maximum dimension or even in the form of finely divided particles. When the solid titaniferous material is added in relatively coarse form, it is advantageous to suspend it in the bath in a graphite basket, but the finely divided solid material may be simply charged directly to the bath where it is readily attacked and evenly distributed continuously through the bath by the bubbling of the added halogenating gas.

'The halogenating gas can be elemental fluorine or chlorine gas or vapors of elemental bromine or iodine. In addition, certain other gases such as carbonyl chloride, carbonyl bromide, or mixtures of chlorine and carbon monoxide, as well as the vapors of the normally liquid carbon tetrachloride, are useful in the practice of my invention. The gas is preferably both anhydrous and oxygen-free and is introduced into the fused salt bath containing the solid particles of titaniferous material through any suitable charging device which will insure uniform dissemination of the gas throughout the bath. For this purpose, I presently prefer to use a graphite tube depending into the bath and provided adjacent its lowermost end with a'plurality of peripheral openings which distribute the halogen gas in all directions into the lower portion of the fused salt bath. At the elevated temperature of the bath, the halogen thus introduced reacts promptly and effectively with the titanium component of the solid titanium carbide material to form a titanium halide which is immediately held in solution by the fused salt. Inasmuch as this reaction and dissolution takes place so effectively that no halogen gas or other halogen vapors are evolved as long as the reaction proceeds, the evolution of free halogen from the bath into the inert atmosphere thereabove may be used as a clear indication of the substantially complete extraction of the titanium component of the solid carbide material.

In general, the halogenation is completed in a period of one to six hours, the length of this period depending inter alia on the degree of subdivision of the solid titaniferous material to be halogenated, the temperature of the bath and the amount of titanium halide to be thus produced in the bath. Although the titanium halide content of the bath is not critical in the practice of the present invention, it is pertinent to note that the titanium halide content of the bath can be readily built up to a level of at least (calculated as titanium) as compared with a maximum titanium content of about 3% in the baths produced during the practice of the methods of the aforementioned Sibert and Burwell applications.

The halogenation of the titanium carbide itself or of the mutual solid solution of titanium carbide and titanium monoxide in the fused halide salt bath converts the titaneum component of the solid carbide material to a titanium halide that dissolves in the fused salt bath, leaving as an undissolved residue of the reaction a carbon regulus having substantially the same physical shape as the original carbide material. That is, where massive slabs or lumps of titanium carbide are used as the solid titaniferous material, the carbon regulusresulting from the halogenation of this: material will retain the same massive slab or lump form. When the titaniferous material is in the form of a powder or small particles, the finely divided carbon regulus resulting from the halogenation operation will tend to float to the surface of the fused salt bath whence it can be removed mechanically by appropriate means. 7 1

The fused salt bathcontaining the titanium halide product is advantageously filtered under an inert atmosphere such as argon through a heated filter of an inert porous material such as porous graphite to remove particles of unreacted solid titaniferous material and of the carbon regulus resulting from the halogenation op-- eration. The resulting fused salt filtrate may be used directly as a feed material in an electrolytic operation, or it may be allowed to solidify and the resulting massive salt product treated by physical and chemical means to recover the transition metal halide component of the salt mixture. For example, where the transition metal product is stable at high temperatures or forms complex double halides with bath constituents that are stable at high temperatures, fractional distillation may be employed as a means of separating the various constituents of the salt bath. In the case of tri-valent transition metal halides, the desired halide salt may be recovered by fractional crystallization of the salt mixture from an aqueousacid solution. In the case of the di-valent transition metal halides which are unstable at high temperatures and which cannot be handled in aqueous solutions. without oxidizing the di-valent transition metal to a higher valent state it is preferable to use the transition metal halide product in the form of a fused salt solution containing this product.

The transition metal halide products in admixture with the fused salt bath in which they are formed are suitable for use as cell feed material in the processes of the aforementioned Sibert and Burwell applications for the electrodeposition of transition metals from fused salt baths. The fused salt bath containing the solid titaniferous material may be halogenated in situ in an electrolytic cell in which electrolysis is subsequently to be carried out. I presently prefer, however, to prepare the fused salt bath containing the titanium halide in a separate reactor vessel and then to transfer the fused salt to the electrolytic cell in which the electrolysis is carried out. The transfer of the fused salt may be carried out through pipes of graphite or other inert material communicating between the halogenation reactor and the electrolytic cell. The electrolytic cell equipment, and the electrolytic conditions such as cell voltage and cathode density for this electrolysis, are the same as set forth in the aforementioned Sibert and Burwell applications. The primary product of the electrolysis is titanium metal which is deposited on the cell cathode either as a recoverable titanium deposit or as a titanium cladding layer on the base metal cathode material. The halogen component of the titanium halide which has previously been formed in the fused salt bath is liberated at the anode and may be readily collected and reused as the halogenatin g agent for the solid titaniferous material as described hereinbefore. The resulting spent cell bath, after completion of this electrolytic decomposition of the titanium halide component of the bath as evidenced by the visible formation of free alkali metal or alkaline earth metal at the cell cathode, is substantially identical with the original fused halide salt in which the titaniferous solid material was halogenated,

lytic cell feed material in processes for electrolytically producing the transition metal in metallic form.

The following examples are illustrative but not limitative of the practice of my invention:

Example I A triple section graphite container was provided, the top and bottom sections of which had a capacity equivalent to about 15 pounds of water and the middle section of which had a. capacity approximately one-third that of the top and bottom sections. The top section was a graphite crucible the bottom of which was provided with a needle valve comprising a pour hole in which fitted a tapered graphite rod extending upwardly out of the top of the crucible. The middle section was a flat bottom graphite crucible the bottom of which was pierced with a multiplicity of fine holes. The bottom section was a graphite crucible having a solid bottom. The abutting top and bottom edges of the three sections were planed smooth to facilitate assembly of the container. After being charged with solid starting materials as described hereinafter, the sections were assembled and the assembled container was placed inside a graphite resistor contained in a metal furnace shell in which an atmosphere of pure argon could be established and maintained. A hollow graphite tube extended through the top of the metal shell into the top section of the container. The bottom of this graphite tube was closed off and the lower portion thereof for the space of about one inch was pierced about its periphery with a multiplicity of fine holes about inch in diameter to permit the introduction of a chlorinating gas into the top section of the graphite container.

Prior to assembly of the graphite container, the middle section thereof was filled with a filter bed of minus 100 mesh petroleum coke rammed tightly into the graphite crucible. The graphite needle valve of the top section was closed and an anhydrous mixture of 1600 grams of potassium titanium fluoride, 8400 grams of sodium chloride, and 400 grams of titanium carbide in the form of 200 mesh powder was placed in this section of the container. The three sections were then assembled together and the assembled container was placed inside the furnace. The argon stream was started and, as soon as all atmospheric oxygen had been flushed from the container, the furnace was heated to 825 C. by passing an electric current through the graphite resistor. At this temperature, the salt constituents of the charge became thinly fluid. Chlorine gas was introduced into the molten salt mixture through the hollow graphite tube described previously at a rate of 230 grams per hour.

After a total of approximately 690 grams of chlorine had been introduced into the molten salt mixture, the chlorination was stopped and the needle valve holding the melt in the top crucible was opened slightly to permit the melt to drain through the carbon filter bed into the bottom section of the container. The furnace was then allowed to cool to room temperature and the graphite container was removed therefrom and disassembled. The carbon filter from the middle section was ignited and the resulting ash was analyzed for titanium to determine the amount of titanium carbide that remained undissolved in the melt.

The analysis of the ash showed a titanium content equivalent to 80 grams of titanium carbide. However, a portion of the titanium content of the ash was due to the presence of potassium titanium fluoride in the carbon filter as a result of the passage of the molten salt mixture through the filter. Therefore, more than 80% of the titanium carbide included in the original charge reacted with the chlorine gas to form soluble titanium chlorides. The solidified salt mixture in the bottom crucible showed a salmon pink color near the bottom of the mass and a pink changing to purple color near the top thereof. Analysis of a portion of this salt mixture indicated the presence of potassium titanium fluoride, sodium chloride and lower valent titanium chlorides.

Example 11 An anhydrous mixture of 1600 grams of potassium titanium fluoride, 8400 grams of sodium chloride and 400 grams of an equimolar mutual solid solution of titanium carbide and titanium monoxide having a particle size of minus 200 mesh was charged to the top section of the graphite container described in Example I. A filter bed of finely divided petroleum coke was rammed into the middle section of the container and the three sections were assembled together as before. The assembled container was placed in the furnace of Example I and an atmosphere of argon gas was established therein. The furnace was then heated to a temperature of 825 C. After the salts in the top section had become molten, 685 grams of chlorine gas were introduced into the molten salt over a period of about 3 hours. On completion of the chlorination step, the furnace was allowed to cool and, after removal from the furnace, the graphite container was disassembled as before.

The carbon filter bed from the middle section was washed with hot water to dissolve the soluble salts contained therein. The carbon and titanium carbide residue were then ignited and the titanium content of the ash determined. The titanium content of the ash was found to be equivalent to 32 grams of the equimolar mutual solid solution of titanium carbide and titanium oxide included in the original charge. Therefore, 92% of the titanium carbide-titanium monoxide material reacted with the chlorine gas to form lower valent titanium chlorides that dissolved in the fused salt mixture.

Example III An anhydrous mixture of 1600 grams of potassium titanium fluoride, 8400 grams of sodium chloride, and 400 grams of minus 200 mesh titanium carbide were introduced into the top section of the graphite container of Example I. The middle section of the container was charged with petroleum coke, the three sections were assembled together, and the assembly was placed in the furnace of Example I as before. After establishing an inert atmosphere within the furnace and after fusion of the salt mixture in the top of the container, 975 grams of phosgene gas were introduced into the fused salt mix over a period of about four hours. After chlorination was stopped, the furnace was allowed to cool and the graphite container was disassembled as before.

The carbon filter bed was washed as in Example II to remove soluble salts, the washed carbon residue was ignited, and the resulting ash was analyzed to determine the titanium content thereof. The analysis indicated that of the titanium carbide originally introduced into the top section had reacted with the phosgene gas to form lower valent titanium chlorides that went into solution in the molten salt mixture.

Example IV An anhydrous mixture of 1600 grams of potassium titanium fluoride, 8400 grams of sodium chloride, and 400 grams of an impure titanium metal containing approximately 96% titanium 10f 4% oxygen and carbon were introduced into the top section of the graphite container described in Example I. After the graphite container had been assembled and the salt mixture had been fused in an inert atmosphere as in Example I, 1225 grams of phosgene gas were introduced into the molten salt over a period of about four hours. After cooling of the furnace, disassembly of the graphite container, and thorough washing of the carbon filter bed, the filter bed was ignited and the resulting ash analyzed to determine the titanium content thereof. The analysis indicated that 94% of the titanium metal included in the original charge had reacted with the phosgene gas to form lower valent titanium chlorides that dissolved in the molten salt mixture.

'Example V An anhydrous mixture of 1600 grams of potassium niobium fluoride, 8400 grams of sodium chloride, and 400 grams of minus 200 mesh niobium carbide were charged into the top of the graphite container and fused in an inert atmosphere in the manner described in Example 1. Over a period of about 2 hours, 372 grams of phosgene gas were introduced into the molten salt mixture. After chlorination was stopped the carbon filter bed from the middle section of the container was thoroughly washed with hot water and the washed carbon residue was ignited as before. Analysis of the ash resulting from the ignition showed that approximately 95% of the niobium carbide reacted with the phosgene gas to form niobium chlorides that dissolved in the molten salt mixture.

Example VI A graphite crucible was provided with a false graphite bottom punctured with a number of small holes and fitted with a graphite tube leading from a central hole in the false bottom to the open top of the crucible. Thecrucible was lined with cubes of titanium carbide weighing a total of 1450 grams and 1800 grams of potassium chloride was charged to the crucible. The charged crucible was then placed in a gas-tight furnace lined with graphite and provided with gas inlet and outlet connections. The interior of the furnace was flushed with argon and the KCl was melted under an inert atmosphere.

When the temperature of the furnace and of the fused KCl reached 850 C., chlorine gas was introduced into the fused salt bath through the graphite tube communicating with the underside of the false bottom of the crucible. The rate of flow of the gas was metered so that substantially all of the chlorine reacted with the titanium carbide lining of the crucible and only a trace escaped from the furnace through the bleed-01f valve. After 2700 grams of the gas had been introduced into the fused salt bath, heavy chlorine fumes were observed escaping through the bleed-off valve indicating completion of the reaction. The chlorination was thereupon stopped and the furnace was allowed to cool. Y

After cooling to room temperature, the solidified salt cake was removed from the crucible. These was no evidence of titanium carbide, the carbide having been converted to a carbon regulus that readily broke away from the salt cake. The salt cake weighted 5400 grams and, upon analysis, was found to be 90% by weight KTiCl Example VI I The graphite crucible of Example VI was lined with cubes of titanium carbide weighing 400 grams. A salt charge of 385 grams of potassium fluoride and 1500 grams of sodium fluoride was introduced into the crucible. Thecrucible was placed in the gas-tight furnace and the salt charge was melted under an inert atmosphere. When the temperature of thef used salt bath reached 875 C., fluorine gaswas introduced thereinto through the graphite tube communicating with the false bottom of the crucible. The flow of fluorine gas was metered so that only a trace of halogen gas escaped through the bleed-01f valve of the furnace. After 400 grams of fluorine had been introduced into the fused salt bath, heavy gas evolution was observed, indicating completion of the fluorination operation. The gas evolved was largely chlorine due to the displacement of chlorine by fluorine in the fused sodium chloride. The fluorination was thereupon stopped and the furnace allowed to cool to room temperature. The salt cake was removed from the crucible and the carbon regulus was broken away from its exterior surface. The salt cake weight about 2500 grams and, on analysis, was found to contain 40% KTiT 10 Example VIII An anhydrous mixture of 1600 grams of sodium chlo*- ride and 400 grams of potassium fluotitanate was charged to a graphite crucible. The graphite crucible was placed in a gas-tight furnace and the salt charge melted under an inert atmosphere. A hollow porous graphite cylinder containing 100 grams of titanium carbide powder was lowered into the fused salt bath. The graphite cylinder was supported by a graphite tube through which gas could be introduced into the interior of the graphite cylinder. When the temperature of the bath reached 875 C. fluorine gas was passed through the supporting graphite tube through the titanium carbide and out into the fused salt bath. Upon completion of fluorination, as indicated by evolution of chlorine gas from the fused salt bath, the fluorine flow was stopped and the furnace allowed to cool to room temperature. The solidified salt cake was thereupon removed from the crucible and found to weigh 2100 grams. Analysis disclosed that the salt cake was 26% KTiF Example IX A graphite crucible containing a titanium carbide slab weighing 1200 grams was charged with 1500 grams of potassium chloride. The crucible was placed within a gas-tight furnace and the salt charge was melted under an inert atmosphere. When the temperature of the fused salt bath reached 1000' C. a flow of chlorine gas was directed through a graphite tube into the carbide slab. After a total of 1800 grams of chlorine had been introduced into the fused salt bath, chlorination was stooped and the furnace allowed to cool to room temperature. The resulting solidified salt cake was thereupon removed from the crucible. Due to the massive form of the titanium carbide, the reaction was not complete and there was some residual titanium carbide present in the salt cake. The salt cake was separated from the residual titanium carbide and carbon regulus and was found to weight 3750 grams. Analysis indicated the salt cake to be substantially all KTiCl This product was extremely hygroscopic and when mixed with water resulted in the liberation of hydrogen gas.

Example X The graphite crucible of Example VI was charged with 1200 grams of lump titanium carbide, and 1500 grams of potassium chloride. The charged crucible was placed within a gas-tight furnace and the salt charge melted under an inert atmosphere. When the fused salt bath reached a temperature of 1000 C. chlorine gas was introduced into the fused salt bath through the tube cornmunicating with the underside of the false bottom of the crucible. After 1550 grams of chlorine had been introduced into the bath heavy evolution of chlorine indicated that the reaction was complete, and, thereupon, the chlorination was stopped. The furnace was then allowed to cool to room temperature and the salt cake was removed from the graphite crucible. After separating the salt cake from the carbon regulus the product was found to weigh 3850 grams and to contain greater than KTiCl From the foregoing description it is apparent that the method of our invention provides a simple and effective way to produce a wide variety of transition metal halides that are useful for many purposes including the preparation of other compounds of these transition metals andparticularly the preparation of the transition metal in pure metallic form.

This application is a continuation-in-part of my application Serial No. 398,192, filed December 14, 1953, now abandoned.

I claim:

1. The method of producing a fused salt electrolyte containing a soluble halide of a transition metal of the group consisting of titanium, zirconium, hafnium, niobium, vanadium and tantalum which comprises forming a fused salt bath composed of at least one halide of the group consisting of alkali metal halides and alkaline earth metal halides, introducing into the fused salt bath a solid transition metal carbide of the group consisting of the carbide of the transition metal and a mutual solid solu tion of the carbide and the monoxide of the transition metal, and introducing into the solid-containing fused salt bath a halogenating gas produced externally of the fused salt bath and selected from the group consisting of fluorine, chlorine, carbonyl chloride, bromine, carbonyl bromide, and iodine while maintaining said bath under a non-contaminating atmosphere and continuing the introduction of the halogenating gas into the bath until the transition metal content of said solid carbide has been substantially completely converted to the halide thereof in solution in the fused salt bath.

2. The method of producing a fused salt electrolyte containing a soluble halide of a transition metal of the group consisting of titanium, zirconium, lhafnium, niobium, vanadium and tantalum which comprises forming a fused salt bath composed of at least one halide of the group consisting of alkali metal halides and alkaline earth metal halides in admixture with an alkali metal double halide of said transition metal, introducing into the fused salt bath a solid transition metal carbide of the group consisting of the carbide of the transition metal and a mutual solid solution of the carbide and the monoxide of the transition metal, and introducing into the solid-containing fused salt bath a halogenating gas produced externally of the fused salt bath and selected from the group consisting of fluorine, chlorine, carbonyl chloride, bromine, carbonyl bromide, and iodine while maintaining said bath under a non-contaminating atmosphere and continuing the introduction of the halogenating gas into the bath until the transition metal content of said solid carbide has been substantially completely converted to the halide thereof in solution in the fused salt bath.

3. The method of producing a fused salt electrolyte containing a soluble halide of a transition metal of the group consisting of titanium, zirconium, hafnium, niobium, vanadium and tantalum which comprises forming a fused salt bath composed of at least one halide of the group consisting of alkali metal halides and alkaline earth metal halides, introducing into the fused salt bath a solid transition metal carbide of the group consisting of the carbide of the transition metal and a mutual solid solution of the carbide and the monoxide of the transition metal, and introducing into the solid-containing fused salt bath a halogenating gas produced externally of the fused salt bath and selected from the group consisting of fluorine, chlorine, carbonyl chloride, bromine, carbonyl bromide, and iodine while maintaining the temperature of the resulting solid-containing fused salt bath Within the range of about 600 to 1100 C. and While maintaining said bath under a non-contaminating atmosphere and continuing the introduction of the halogenating gas ito the bath until the transition metal content of said solid transition metal carbide has been substantially completely converted to the halide thereof in solution in the fused salt bath.

4. The method of producing a fused salt electrolyte containing a soluble titanium di-halide which comprises forming a fused salt bath composed of at least one halide of the group consisting of alkali metal halides and alkaline earth metal halides, introducing into the fused salt bath a solid product containing titanium carbide, and introducing into the solid-containing fused salt bath a halogenating gas of the group consisting of fluorine, chlorine, carbonyl chloride, bromine, carbonyl bromide, and iodine while maintaining the temperature of the resulting solid-containing fused salt bath within the range of about 900 to 1100 C. and While maintaining saidbath under a non-contaminating atmosphere and continuing the introduction of the halogentating gas into the bath until the titanium content of said solid product has been 12 substantially completely converted to the di-halide thereof in solution in the fused salt bath.

5. The method of producing a fused salt electrolyte containing a soluble titanium tri-lhalide which comprises forming a fused salt bath composed of at least one halide of the group consisting of alkali metal halides and alka line earth metal halides, introducing into the fused salt bath a solid product containing titanium carbide, and introducing into the solid-containing fused salt bath a halogenating gas produced externally of the fused salt bath and selected from the group consisting of fluorine, chlorine, carbonyl chloride, bromine, carbonyl bromide, and iodine while maintaining the temperature of the resulting solid-containing fused salt bath within the range of about 700 to 900 C. and while maintaining said bath under a non-contaminating atmosphere and continuing the introduction of the halogenating gas into the bath until the titanium content of said solid product has been substantially completely converted to the tri-halide thereof in solution in the fused salt bath.

6. The method of forming a fused salt bath containing a chloride of a transition metal of the group con= sisting of titanium, zirconium, hafnium, niobium, vana dium and tantalum and capable of being electrolyzed in the fused state with the resulting cathodic deposition of the transition metal which comprises fusing at least one halide salt of the group consisting of alkali and alkaline earth metal halides, introducing into the fused salt a solid product of the group consisting of a carbide of the transition metal and a mutual solid solution of the carbide and the monoxide of the transition metal, and introducing chlorine gas produced externally of the fused salt bath into the resulting solid-containing fused salt While maintaining said bath under a non-contaminating atmosphere and continuing the introduction of the chlorine gas into the bath until the transition metal content of said solid product has been substantially completely converted to the chloride thereof in solution in the halide salt in the form of a fused salt bath.

7. The method of forming a fused salt bath containing a chloride of a transition metal of the group consisting of titanium, zirconium, hafnium, niobium, vanadium and tantalum and capable of being electrolyzed in the fused state with the resulting cathodic deposition of the transition metal which comprises fusing at least one halide salt of the group consisting of alkali and alkaline earth metal halides, introducing into the fused salt a solid product of the group consisting of a carbide of the transition metal and a mutual solid solution of the carbide and the monoxide of the transition metal, and introducing carbonyl chloride gas produced externally of the fused salt bath into the resulting solid-containing fused salt while maintaining said bath under a non-contaminating atmosphere and continuing the introduction of the carbonyl chloride gas into the bath until the transition metal content of said solid product has been substantially completely converted to the chloride thereof in solution in the [halide salt in the form of a fused salt bath.

8. The method of producing a transition metal of the group consisting of titanium, zirconium, hafnium, niobium, vanadium and tantalum which comprises fusing at least one halide salt of the group consisting of alkali and alkaline earth metal halides, introducing into the fused salt a solid product of the group consisting of a carbide of the transition metal and a mutual solid solution of the carbide and the monoxide of the transition metal, introducing into the solid-containing fused salt bath a halogenating gas produced externally of the fused salt bath and selected from the group consisting of fluorine, chlorine, carbonyl chloride, bromine, carbonyl bromide, and iodine while maintaining said bath under a non-contaminating atmosphere and continuing the introduction of the halogenating gas into the bath until the transition metal content of said solid product has been 13 substantially completely converted to the halide thereof in solution in the halide salt in the form of a fused salt bath, and electrolyzing the resulting fused salt bath in the presence of a carbonaceous anode to effect electrodeposition of the transition metal component of the transition metal halide.

9. The method of producing a transition metal of the group consisting of titanium, zirconium, hafnium, niobium, vanadium and tantalum which comprises fusing at least one halide salt of the group consisting of alkali and alkaline earth metal halides, introducing into the fused salt a solid product of the group consisting of a carbide of the transition metal and a mutual solid solution of the carbide and the monoxide of the transition metal, introducing an externally produced ohlorinating gas of the group consisting of chlorine and carbonyl chloride into the resulting solid-containing fused salt while maintaining said bath under a non-contaminating atmosphere and continuing the introduction of the halogenating gas into the bath until the transition metal content of said solid product has been substantially completely converted to the chloride thereof in solution in the halide salt in the form of a fused salt bath, electrolyzing the resulting fused salt bath in the presence of a carbonaceous anode to effect electrodeposition of the transition metal component of the transition metal chloride, and using the resulting spent electrolyte as the fused salt in which the solid transition metal product is chlorinated.

10. The method of producing a fused salt electrolyte containing a soluble titanium dihalide which comprises: forming a fused salt bath composed of at least one halide of the group consisting of alkali metal halides, alkaline earth metal halides and mixtures of same with an alkali metal double halide of titanium, introducing into the fused salt bath a solid product containing titanium carbide, and introducing into the solid-containing fused salt bath a halogenating gas produced externally of the fused salt bath and selected from the group consisting of fluorine, chlorine, carbonyl chloride, bromine, carbonyl bromide and iodine while maintaining the temperature of the resulting solid containing fused salt bath within the range of about 900 to 1100 C. and while maintaining said bath under a non-contaminating atmosphere and continuing the introduction of the halogenating gas into the bath until the titanium content of said solid product has been substantially completely converted to the dihalide thereof in solution in the fused salt bath.

11. The method of producing a fused salt electrolyte containing a soluble titanium trihalide which comprises: forming a fused salt bath composed of at least one halide of the group consisting of alkali metal halides, alkaline earth metal halides and mixtures of same with an alkali metal double halide of titanium, introducing into the fused salt bath a solid product containing titanium carbide, and introducing into the solid-containing fused salt bath a halogenating gas produced externally of the fused salt bath and selected from the group consisting of fluorine, chlorine, carbonyl chloride, bromine, carbonyl bromide and iodine while maintaining the temperature of the resulting solid containing fused salt bath within the range of about 700 to 900 C. and while maintaining said bath under a non-contaminating atmosphere and continuing the introduction of the halogenating gas into the bath until the titanium content of said solid product has been substantially completely converted to the trihalide thereof in solution in the fused salt bath.

12. The method of producing a fused salt electrolyte containing a soluble halide of a transition metal of the group consisting of titanium, zirconium, hafnium, niobium, vanadium and tantalum which comprises forming a fused salt bath composed of at least one halide salt of the group consisting of alkali metal halides and alkaline earth metal halides, introducing into the fused salt bath a solid transition metal carbide of the group consisting of the carbide of the transition metal and a mutual solid solution of the carbide and monoxide of the transition metal, and introducing an externally derived halogenating gas into the resulting solid-containing fused salt bath while maintaining said bath under a non-contaminating atmosphere and continuing the introduction of the halogenating gas into the bath until the transition metal content of said solid carbide has been substantially completely converted to the halide thereof in solution in the fused bath.

References Cited in the tile of this patent UNITED STATES PATENTS 1,179,394 Barton Apr. 18, 1916 1,814,393 Low July 14, 1931 2,722,509 Wainer Nov. 1, 1955 FOREIGN PATENTS 334,475 Germany Mar. 14, 1921 679,419 Great Britain Sept. 17, 1952 164,283 Australia Apr. 8, 1954 OTHER REFERENCES Transactions of The Electrochemical Society, vol. 87 (1945), pages 551-567, paper by Kroll. 

1. THE METHOD OF PRODUCING A FUSED SALT ELECTROLYTE CONTAINING A SOLUBLE HALIDE OF A TRANSITION METAL OF THE GROUP CONSISTING OF TITANIUM, ZIRCONIUM, HAFNUIM, NIOBIUM, VANADIUM AND TANTALUM WHICH COMPRISES FORMING A FUSED SALT BATH COMPOSED OF AT LEAST ONE HALIDE OF THE GROUP CONSISTING OF ALKALI METAL HALIDES AND ALKALINE EARTH METAL HALIDES, INTRODUCING INTO THE FUSED SALT BATH A SOLID TRANSITION METAL CARBIDE OF THE GROUP CONSISTING OF THE CARBIDE OF THE TRANSITION METAL AND A MUTUAL SOLID SOLUTION OF THE CARBIDE AND THE MONOXIDE OF THE TRANSITION METAL, AND INTRODUCING INTO THE SOLID-CONTAINING FUSED SALT BATH A HALOGENATING GAS PRODUCED EXTERNALLY OF THE FUSED SALT BATH AND SELECTED FROM THE GROUP CONSISTING OF FLUORINE, CHLORINE, CARBONYL CHLORIDE, BROMINE, CARBONYL BROMIDE, AND IODINE WHILE MAINTAINING SAID BATH UNDER A NON-CONTAMINATING ATMOSPHERE AND CONTINUING THE INTRODUCTION OF THE HALOGENATING GAS INTO THE BATH UNTIL THE TRANSITION METAL CONTENT OF SAID SOLID CARBIDE HAS BEEN SUBSTANTIALLY COMPLETELY CONVERTED TO THE HALIDE THEREOF IN SOLUTION IN THE FUSED SALT BATH. 